Field of the Invention
The present inventive subject matter relates generally to the art of functional and/or decorative flakes and/or the production thereof. Particular but not exclusive relevance is found in connection with high aspect ratio metal flakes for use in dispersions and/or suspensions, e.g., such as in inks, pigments, coatings and the like. It is to be appreciated however that aspects of the present inventive subject matter are also equally amenable to other like applications.
Description of Related Art
Conventionally, metal flakes have been formed by vapor depositing a thin layer of metal, e.g., aluminum (Al), on a polyethylene terephthalate (PET) carrier. Commonly, the carrier would first be provided with a release coating to facilitate subsequent removal of the metal from the carrier. Additionally, the release coating could also act as stabilizer, e.g., for the resulting Al flakes. In any event, this release coating is typically applied to the carrier as a solvent-based resin solution. After application, the solvent is evaporated or otherwise driven off, e.g., by heating in an oven, to form a polymer release coating on a surface of the carrier. The thin metal layer is then vapor deposited over the resulting release coating.
Commonly, to create the metal flakes, the thin metal layer is ultimately scraped and/or stripped from the carrier, e.g., with a doctor blade or another appropriate mechanical abrasion tool. To aid in separating the metal from the carrier during the stripping process, a solvent (e.g., such as acetone or the like) is again commonly used, this time to swell, soften and/or dissolve the release coating formed between the metal layer and the carrier. Typically, the metal film is broken into particles by the stripping process and the particles may be further sized and/or refined in later milling and/or other suitable processing steps. Metal flakes produced by this process have been used in printing applications, e.g., such as inks, and may often have a particle size from about 4 to about 12 microns and a thickness from about 150 to about 250 angstroms. The flakes can generally have a smooth mirror-like surface and a high aspect ratio, and coatings made from these flakes typically have a high specular reflectance and a low diffuse reflectance.
The aforementioned process, however, can have certain drawbacks and/or limitations. For example, after use, the carrier is generally undesirable waste material. Moreover, the use of solvents which may contain volatile organic compounds (VOCs) in the formation of the release coating and in the stripping process can be undesirable for environmental and/or other reasons.
Accordingly, a new and/or improved release coating and/or process for producing functional and/or decorative flakes is disclosed which addresses the above-referenced problem(s) and/or others.